1. Field of the Invention
The invention relates to a continuously variable transmission belt wrapped around a driving pulley and a driven pulley, and to a continuously variable transmission having such a continuously variable transmission belt.
2. Description of the Related Art
Generally, a transmission is provided on a power transmission path from a motive power source of a vehicle to wheels. As such a transmission, a belt type continuously variable transmission is known. This belt type continuously variable transmission is constructed by wrapping a belt on a driving pulley and a driven pulley, and performs power transmission between the driving pulley and the driven pulley via the belt. By controlling the wrap-around radii of the belt on the driving pulley and on the driven pulley, the continuously variable transmission controls the speed change ratio between the driving pulley and the driven pulley. An example of the driving belt used in the belt type continuously variable transmission is described in Japanese Patent Publication No. 2-22254. The driving belt described in Japanese Patent Publication No. 2-22254 has a carrier made up of a band combination composed by superimposing endless bands on one another, and many metallic cross members that are slidably mounted on the carrier. Each cross member has a neck portion, and two recesses are formed on both sides of the neck portion.
Incidentally, a lubrication device for a belt type continuously variable transmission that has a continuously variable transmission belt is described in Japanese Patent Application Publication No. 10-141459 (JP-A-10-141459). In Japanese Patent Application Publication No. 10-141459 (JP-A-10-141459), oil feed nozzles for supplying lubrication oil to the belt are disposed on both the input pulley side and the output pulley side. The belt has rings and elements. As the belt is driven, relative sliding between the rings and the elements occur, so that friction heat is generated on the contact surfaces. Therefore, by supplying lubrication oil from the oil feed nozzles to the friction heat generating portions, the friction heat generating portions can be lubricated, so that friction heat becomes relatively unlikely to be generated.
In the case where the lubrication of the belt described in Japanese Patent Application Publication No. 10-141459 (JP-A-10-141459) is performed in a belt type continuously variable transmission having a belt described in Japanese Patent Publication No. 2-22254, lubrication oil is not easily supplied deeply into the dents of the elements, that is, to the vicinity of the neck portion of each element. Therefore, the friction coefficient in the width direction of the carrier is higher in the interior-depth side of each dent, that is, regions near the neck portions, than in regions apart from the neck portions. As a result, there is a possibility of decline in the centering performance of the carrier in the width direction of the dents; for example, the line of the center of the carrier in the width direction may deviate from the line of the center of the driving belt in the width direction in a plane viewed from an outer periphery side of the carrier, or bands constituting the carrier tilt with each other.